Methods for casting hollow ingots

ABSTRACT

An apparatus and method are provided for producing hollow castings wherein an axial tube of metal inserted in a mold and molten metal is poured in the area between the tube and mold to form a metallurgical bond with the tube.

United States Patent 1191 Kocks et al.

[ METHODS FOR CASTING HOLLOW INGOTS [75] Inventors: Friedrich Kocks; Hans J. Lippert,

- both of Dusseldorf, Germany 173 As'signee: Frie drick Kocks, Dusseldorf, Germany- [22] Filed: July 15, 1970 211 Appl. No.: 55,177

[30] I Foreign Application Priority Data [56] ReferencesCited- UNITED STATES PATENTS 2,025,336 '12/1935 Brearley ..164 369x [111 3,73,7@@ 1 51 May 29, 1973 1,391,675 9 1921' Emery ..164/126 1,889,671 11/1932 Koehn ..164/126 x 2,248,693 7/1941 Bartscherer .....164/126 x 2,344,020 3 1944 Boucher 164/1 16 1,061,760 5/1913 Lash ..164/120x 3,220,071 11/1965 Dettore 164/367 x 1,938,276 12/1933 B611 ..164/7-1 371,719 10/1887 Very ..164 332 x 3,206,808 9 1965 Robinson... ..164/96 x 301,233 7/1884 Hauck ....164/111 x 1,527,729 2/1925 Dunajeff ....164/298 x 2,274,580 2 1942 Bailey.... ....l64/348 x 3,414,044 12/1968 Justus ..164/114 x Primary Examiner-J. Spencer Overholser Assistant ExaminerJohn S. Brown AztorneyBuell, Blenko & Ziesenheim [5 7] ABSTRACT An apparatus and method are provided for producing hollow castings wherein an axial tube of metal inserted in a mold and molten metal is poured in the area between the tube and mold to form a metallurgical bond with the tube.

15 Claims, 4 Drawing Figures PATENTEU HAYZ 9 I973 3:7 35 798 SHEET 3 OF 3 mvsmons Friedric cks 8 Hon Jooc Lipper? 1 METHODS FOR CASTING HOLLOW INGOTS This invention relates to methods and apparatus for casting hollow ingots and particularly, to a method for casting hollow ingots especially suited as blanks for seamless pipe and tube production and to an apparatus for applying this method.

It iswell known to cast hollow ingots by the use of axial cores within a cylindrical mold in which molten metal is cast around the core. There are, unfortunately, many disadvantages to the use of this method. Perhaps the greatest disadvantage of this method however, is that removing the core from the inside of the cast ingot is very difficult. Furthermore, due to the fact that casting technique requires the core to be tapered, further processing of the tube blank in the rolling mill creates 1 difficulties. Working with a core, when producing longer hollow blanks is very difficult since the cores are made outof relative light material and therefore very unstable. In addition to above, the use of cores in casting processess is connected with substantial expenditures.

It is further known to produce-pipe blanks with the centrifugal casting method, especially where the pipe is made of high alloy materials, which are very difficult to roll on a rotary piercing mill. The centrifugal casting method, however, allows only the production of relative short and thin-walled tube blanks. Tube blanks produced with the centrifugal casting method show quite frequently segregation areas at the inside, which is of great disadvantage for further processingof a blankin the tube mill.

' The purpose of the present invention is to provide a method and a device which would allow one to produce hollow ingots, especially long tube blanks, in a simple manner, and which are free of segregation areas at the inside.

According to the method of this present invention the problems of the prior art practices are solved by the steps of placinga metal tube in the center of the ingot mold, the tube havingan inside diameter equal to the inside diameter of the tube blank '0 be produced, and

' pouring the molten metal into't e annular area between the ingot mold wall and thd inserted tube.

During the casting operation, the outside of the inserted tube will weld to thecast material and become part of the casting. This way it is possible to case a hollow ingot with a smooth inside free of sand or other refractory and free of surface defects. Segregation in the casting if it exists is only found in the body of the casting" and not on the surface and therefore will have no harmful effects during rolling. With this method it is also possible to produce long hollow ingots of uniform geometric form which have also a favorable homogenous structure over theentire ingot length in the areas most critical for rolling. Furthermore, the invented method allows relative high casting speeds.

. In order to prevent the inserted tube from being heated too much during pouring of the metal, and to eliminate the possibility that the inserted tube might start to melt, the inside wall of the inserted tube should be cooled. Cooling, however, should only be applied in such a way that the outside of the inserted tube still can weld to the ingot.

In order to produce a casting consisting of homogenous material, the inserted .tube is to be of the same material as the casting to be produced.

The inserted tube can be made out of sheet or plate.

In certain cases it can be also of advantage to have a casting which has certain specific properties on the outside. In order to do that, the ingot mold can be provided with a plate or sheet lining consisting of the same material as the inserted tube or of some other desired material. If plated castings have to be produced, depending on the specific application, the inner plating and/or the inserted tube can consist of the plating material. This method is of special importance when pipes or tubes with a corrosion resistant surface layer at the inside and/or the outside have to be produced.

According to the present invention the melt can be poured from the top into a standing ingot mold or from the bottom using any of the known bottom pouring techniques.

Cooling of the inserted tube can be done in various ways. It is of special advantage to use cooling gas, which is directed through the inserted tube. It is, however, also possible to use another coolant medium, for example water. When using a liquid cooling medium, the inserted tube has to be cooled only in an area extending as high as the level of the melt in the ingot mold. Through application of coolant medium the melt can rapidly solidify in this area before the cast ingot and the inserted tube have welded together.

Since, however, the cooling zone moves upwards following the rising level of the poured melt, the ingot will start to heat up again from the inside to the border zones after cooling has been stopped, and thus will bring about a complete interwelding of the ingot and the inserted tube.

In order to make use of the advantages of the centrifugal casting process and to lowerthe specific pressure on the inserted tube, the melt can be centrifuged in the ingot mould. If centrifugation is to be used, it is advisable to centrifuge right from the beginning of the pouring process.

The molten metal can be centrifuged around a vertical axis of the ingot mould. I

It is also possible to centrifuge the melt around a horizontal axis or any other axis forming an angle against the horizontal axis. In this case the molten metal can be channeled into the ingot mould with a pouring spout, a well known casting tool. The molten metal flowing out of the pouring spout can be poured directly onto the inserted tube.

If a vertically erected ingot mould is used, the mould can be covered after pouring and turnedinto a horizontal position. This method is especially advantageous where high casting speeds are used and the melt will only solidify after the ingot mould is in horizontal position. The result of this process are very homogenous castings free of surface defects and fiber cavities.

Since considerable length shrinkage can take place when casting long ingots, vibrations can be applied at the ingot mould in order to loosen the casting from the I provisions are made for support of the inserted tube.

Since the inserted tube is subject to substantial temperature increases, and therefore considerable changes in its length can take place, it is preferred to clamp the inserted tube at one end of the ingot mold, while the other end is supported in a floating clamp head with its thrust direction pointing away from the ingot mold. When using vertically erected ingot moulds, the clamp head taking the thrust load is preferably arranged at the upper end of the ingot mould.

In order to add additional stability to the inserted tube, it can be braced at several places over its entire length, whereby the braces should consist of the same material as the molten metal, thus assuring they will weld to and integrate into the melt.

For cooling of the inserted tube, a cooling device which can be moved vertically in sequence with the pouring speed can be placed inside the ingot mould, having a diameter smaller than the diameter of the inserted tube. The cooling device can be a nozzle ring located at the end of the rod which can be moved in the longitudinal direction of the ingot mold, and at. the same time is used to channel in the cooling medium, as for example cooling water or cooling gas.

In thecase of a vertically erected ingot mould this cooling device can be a circular'plate mounted in a plane at a right angle to the ingot mould axis and movable by a rod or rope in axial direction, whereby at the upper end of the inserted tube an inlet opening for cooling water can be provided. In order to provide an outlet for this cooling water, the circular plate can have openings at the side and/or throiigh holes.

Furthermore, the lower endof the inserted tube can be built so that it is fully or partially closed, and thus is completely filled with cooling water, or alternatively so that the cooling water will flow through it.

In order to avoid damage on the ingot mould walls during casting, the pouring ladle can be provided with a pouring spout adaptable to the length of the mould, and with a spray hood attached to the end, while the ingot mould and the pouring ladle are both movable in direction of the ingot mould axis. The relative motion between the pouring ladle having a pouring nozzle and the ingot mould can be controlled automatically, depending on the upwards speed of the melt in the ingot mould.

In the situation where the ingot mould is arranged horizontally or at an angle against the horizontal position, a pouring spout, movable in the axial direction of the ingot mould and parallel to this axis can be provided, arranged above the inserted tube.

In the foregoing general description of this invention certain objects, purposes and advantages of the invention are set out. Other objects, purposes and advantages will be apparent from a consideration of the following description and the accompanying drawings in which:

FIG. 1 is a vertical section through a device according to this invention with the ingot mold in the vertical position.

FIG. 2 is a vertical section through a second embodiment of the invention.

FIG. 3 is a section on the Line III-III of FIG. 2.

FIG. 4 is a section through a third embodiment of the device of this invention with the ingot mold tilted at an angle to the horizontal.

Referring to the drawings and particularly to FIG. 1 there is illustrated a vertically arranged ingot mold into which molten metal is poured from a ladle 14 above the ingot mould. The pouring ladle 14 has been provided with a pouring nozzle 16, its length depending on the height of the ingot mould, and has at its end a spray hood 18. This device can be built so that the ingot mould is fixed, while the pouring ladle can be moved vertically, or the pouring ladle can be mounted fixed and the ingot mould being movable, for example being lowered into a floor excavation.

The relative movement between the pouring ladle 14 and the ingot mould 12 can be controlled in dependence of the upward speed of the molten metal l0 in the mould. As control device a float gauge can be provided. This gauge is not shown on the drawing, but it is a well known and widely used device. By arranging pouring nozzle 16 and at its end spray head 18, the ingot mould wall is well protected against squirting metal. In order to achieve maximum protection against squirting or spraying metal, the device should be moved so that the spray hood is always held at minimum distance above the molten metal 10 in the ingot mould.

A metal tube 22 has been placed exactly in the center of the ingot mould 12, parallel to the ingot mould axis and extending over the entire length of the ingot mould or the hollow casting to be produced, and which during casting operation or right after pouring will weld to the other material. The inside diameter of the inserted tube 22 corresponds to the inside diameter of the hollow ingot to be cast.

At least the top and bottom end of the inserted tube 22 are supported by the ingot mold 12. The bottom end of the tube 22 is held by a suitable clamping device, for example a clamp ring 24 or clamp jaws, while the upper end of the inserted tube is held by a clamp head 26 which is movable in the axial direction.

In the case where the inserted tube 22 corresponds exactly in its length to the length of the casting to be produced, as shown in FIG. 1, the clamping devices 24 and 26 reach into the inserted tube 22 and clamp it there.

In order to allow for especially tight clamping of the inserted tube 22, especially when the inserted tube 22 could lose part of its stability by heating up during operations, clamping devices can be used which can hold the tube inside and outside.

The vertically movable clamp head 26 holding the top end of the inserted tube 22 is supported by a guide 32 whereby this guide is held by rigid arms 34 which areconnected to the ingot mould 12. At the upper end of the clamp head 26 a pulling device 36 is attached which will hold the clamp head during the entire operation under tension, with the direction of thrust pointing away from the ingot mould. A constant load can be obtained for example by connecting a wire rope, or a chain or similar equipment to the clamp head, and which is at first brought up vertically, then turned by the rolls 38 in opposite direction and provided with a weight 40 at its end.

This provision will bring the inserted tube 22 under constant tension, and any changes in length resulting from the heating up, or later on from cooling of the same, can be compensated for. It is, however, not necessarily required to have the inserted tube under tension. Instead of a clamping device, guides could be used at the upper end of the inserted tube, which would allow changes in length of the inserted tube. Such guides, which would be mainly used for centering the inserted tube, can be located at the inside and/or the outside of the inserted tube.

Besides the clamping devices or guides described above, braces can be arranged at certain places over the length of the inserted tube, which should consist of the same material as the molten metal and which would give additional support to the inserted tube and hold same on center. Such braces, not shown on attached drawing, are of special importance for ingot moulds arranged horizontally, or under an angle to the horizontal, since the middle portion of the inserted tube would have a certain amount of deflection in such arrangements.

The tubes 22 inserted into the ingot mould have to absorb a high amount of heat from the melt l0, and have to have a sufficient wall thickness in order to avoid melting of these tube walls. For economical reasons it is desirable to use the thinner walls. In order to apply this successfully, the inside wall of the inserted tube has to be cooled. Cooling, however, should only be applied so that the outer wall of theinserted tube will still form a welded union with the casting to be produced.

Cooling of the inserted tube can be done in several ways. For example, cooling gas can be circulated through the inserted tube, or a liquid cooling medium can be used, which will flow. through the inserted tube,

' or the inserted tube can be filled with a liquid coolant,

whereby the steam developing can escape at the top. When using a method where the liquid is circulating through the inserted tube it'can be arranged so that the liquid dribbles down at the inside wall of the tube, or that enough liquid is pumped in from the top of the inserted tube to fill it entirely, and whereby the liquid could exit at the bottom end of the tube which is opened fully or only partially. In'case the inserted tube should always be filled with a cooling liquid, the bottom of the inse'rtedtube can be closed completely, or provided with a drain pipe 42. The amount of liquid lost through steam generated, and/or flown through exit pipe 42 can be replaced by cooling liquid supplied through inlet pipe 44 arranged at the upper end of the inserted tube 22. The best suited coolant liquid is water, since it is available in sufficient quantity and not very expensive.

FIG. 1 to 3 of the attached drawings show cooling devices whereby the inserted tube is cooled during casting operations only in an area around the level of the molten metal. In this area, where the metal is still liquid, the greatest heat transfer takes place, and thus the inserted tube is under the heaviest heat load there. It is, however, very important to cool very intensively in this area in order to solidify the metal around the inserted tube as fast as possible. Thereby it is possible to cool so intensively that similar to the continuous casting process, the tube 22 will not weld to the metal 10. A welding together of the tube and metal will take place later after the cooling device has been moved out-of this area, following the rising metal level, and the outer zones of the casting are heated up again from the inside.

Referring specifically to the cooling device of FIG. 1 there is shown a cooling device consisting of a ring 48 with outlet openings 46 arranged at the end of a movable bar 50. The coolant medium is thereby supplied through the bar50. Suitable coolant mediums are cooling gas or coolant liquid, whereby cooling liquid which has not been transformed to steam, can exit at the bottom of theingot mold 12 through exit pipe 42.

If the ingot mold 12 as shown for example in FIG. 1 is built so that it can be lowered, the pouring ladle 14 with pouring nozzle 16 and the cooling device are arranged in fixed position. In case the ingot mould is arranged in fixed position, the pouring ladle l4 and the bar 50 with nozzle ring 48 are arranged movable, whereby the motions of pouring ladle l4 and bar 50 can be in tandem.

In the case of FIG. 2 there is illustrated a vertical mold arrangement similar to that of FIG. 1 with like parts bearing like numbers with the suffix (a). In this embodiment the inserted axial tube 22a is larger than the mould 12a and the bottom clamping device 28 and the top clamping head 30 clamp the inserted tube 22 from the outside as shown. The other parts of this embodiment operate as described in connection with FIG. 1, except for the cooling device which consists of a circular plate 52 arranged at a right angle to the ingot mold axis and is movable in the axial direction of the ingot mould, pulled by a bar or rope 54. The relative motion between the cooling device and the ingot mould can take place similar to the example shown in FIG. 1. In the cooling device shown in FIG. 2 and 3 only the section around the molten metal level in the ingot mould is cooled. Water as cooling liquid is supplied through inlet pipe 440 arranged at the upper end of the ingot mould, into the inserted tube 22a thus creating a water column 56 above circular plate 52. It is advisable to keep the water-column somewhat higher than the level of the molten metal, in order to guarantee intensive cooling of the tube section most endangered by the high heat load. Through notches 58 at the circumference of the circular plate 52 and/or holes 60, the cooling liquid can escape and flow out through exit pipe 420 arranged at the bottom of the ingot mould 12a. The water column 56 can be held almost constant through additional supply of cooling water. After the circular plate 52 approaches the upper end of the inserted tube 22d the water supply is stopped and the water column 56 above the circular plate can flow out, thus avoiding that the cooling water would flow out over the upper end of the inserted tube 22a.

The vertically erected ingot mould 12 or 12a shown in FIGS. l and 2 can be built so that it can rotate around its axis, whereby the pressure on the inserted tube 22 or 22a would be lowered. If this revolving arrangement for ingot mould 12 or is used, the braces 24 or 24a which hold clamp head 26 or 30 cannot be used, since they would interfere with pouring nozzle 16 or 16a when rotating. The clamp head 26 or 26a therefore has to be supported by a bearing which is arranged fixed in relation to the rotating ingot mould.

Furthermore, the ingot mould can be covered immediately after pouring and moved into horizontal position, thereby lowering the danger of cracking, especially for long castings. In order to support the shrinking process during cooling, the ingot mould can be subjected to vibrations during that period.

According to another arrangement of the invented device, according to FIG. 4, the ingot mould 62 is arranged in almost horizontal position. The ingot mould is supported by rollers 64 and can be rotated. As in normal centrifugal casting operations, liquid metal is supplied through a pouring spout 66.

As in the other examples described above, a tube 68 has been arranged in the center of the ingot mould 62 which is held by a clamping device 72 arranged at the bottom end of the ingot mould 62 which is closed by cover 70. The other end of the inserted tube 68 can be held by a revolving clamp head, which in turn is held by a fixed support. This arrangement is not shown on the drawing.

The pouring spout 66 reaching into the ingot mould is arranged so that the liquid metal leaving the pouring spout is poured directly onto the inserted tube 68 and there partially solidifies. The metal still liquid is forced by the centrifugal forces of the rotating ingot mould to flow in direction of the ingot mould wall.

The pouring spout 66 is arranged movable in axis direction of the ingot mould, whereby the relative motion between pouring spout 66 and ingot mould 62 can be controlled depending on the liquid metal level in the ingot mould.

The inserted tube 68 in the example shown in FIG. 4 of the invented device can also be kept under tension during the casting process.

In case homogenous hollow castings must be produced, inserted tubes consisting of the same material as the casting to be produced have to be used. If sufficient cooling of the inserted tube can be provided, this tube can be made out of thin plate for economical reasons.

In order to take full advantage of this casting method, plate coatings 74 can be used in all examples described above. This plate coating 74 is placed around the inside of the ingot mould before the casting process takes place, and will weld to the casting itself.

In case plated castings should be produced, for example to produce pipes with corrosion resistant and/or acid-proof surfaces, tube inserts and/or plate coatings can be used consisting of a material with the desired properties.

While certain preferred embodiments and practices of this invention have been illustrated and described in the foregoing specification, it will be understood that this invention may be otherwise embodied.

We claim:

1. The method of producing hollow castings comprising the steps of:

a. inserting an axial tube of compatible metal axially of a mold, said tube having an inside diameter substantially equal to the inside diameter of the hollow casting to be produced, and

b. pouring molten metal into the area between the mold and the tube at a temperature sufficient to cause fusion and metallurgical bonding between the metal and the outside wall of said tube,

c. cooling the inside wall of said tube during the casting operation only in an area around the level of the molten metal in the ingot mold at a rate such that metallurgical bonding of the metal with the outside wall of the tube occurs while the inside wall remains intact at all times. I

2. The method of producing hollow castings comprising the steps of:

a. inserting an axial tube of compatible metal axially of a mold, said tube being of the same material as the hollow casting to be produced, and having an inside diameter substantially equal to the inside diameter of the hollow casting to be produced, and

b. pouring molten metal into the area between the mold and the tube at a temperature sufficient .to cause fusion and metallurgical bonding between the metal and the outside wall of said tube, and

c. cooling the inside wall of said tube during the casting operation only in an area around the level of the molten metal in the ingot mold at a rate such that metallurgical bonding of the metal with the outside wall of the tube occurs while the inside wall remains intact at all times.

3. The method of producing hollowing castings comprising the steps of:

a. inserting an axial tube of compatible metal axially of a mold, said tube having an inside diameter substantially equal to the inside diameter of the hollow casting to be produced,

b. inserting into the mold a sheet metal lining of the same material as the axial tube,

c. pouring molten metal into the area between the mold and the tube at a temperature sufficient to cause fusion and metallurgical bonding between the metal and the outside wall of said tube, and

d. cooling the inside wall of said tube at a rate such that metallurgical bonding of the metal with the outside wall of the tube occurs while the inside wall remains intact at all times.

4. The method according to claim 5 wherein the axial tube is formed of a plating material different from the hollow casting to be produced and the mold includes a sheet metal lining of the same plating material as the axial tube.

5. The method according to claim 1 wherein cooling gas is channelled through the inserted tube.

6. The method according to claim 1 wherein cooling is applied by using a liquid cooling medium.

7. The method according to claim 10 wherein water is used as cooling medium.

8. The method according to claim 1 wherein the inserted tube is cooled during the casting operation only in an area around the level of the molten metal in the ingot mould.

9. The method according to claim 1 wherein the molten metal is centrifuged in the ingot mould.

10. The method according to claim 1 wherein the molten metal is centrifuged in the ingot mould from the beginning of the pouring operation.

11. The method according to claim 10 wherein the melt is centrifuged around a vertical axis.

12. The method according to claim 10 wherein the melt is centrifuged around a generally horizontal axis.

13. The method according to claim 12 wherein the molten metal is channelled into the rotating ingot mould through a pouring spout onto the inserted tube.

14. The method according to claim 1 wherein the ingot mould is covered up after completion of pouring and tilted into a horizontal position.

15. The method according to claim 1 wherein the axial tube is held under tension during the entire casting process.

0 I t i t 

1. The method of producing hollow castings comprising the steps of: a. inserting an axial tube of compatible metal axially of a molD, said tube having an inside diameter substantially equal to the inside diameter of the hollow casting to be produced, and b. pouring molten metal into the area between the mold and the tube at a temperature sufficient to cause fusion and metallurgical bonding between the metal and the outside wall of said tube, c. cooling the inside wall of said tube during the casting operation only in an area around the level of the molten metal in the ingot mold at a rate such that metallurgical bonding of the metal with the outside wall of the tube occurs while the inside wall remains intact at all times.
 2. The method of producing hollow castings comprising the steps of: a. inserting an axial tube of compatible metal axially of a mold, said tube being of the same material as the hollow casting to be produced, and having an inside diameter substantially equal to the inside diameter of the hollow casting to be produced, and b. pouring molten metal into the area between the mold and the tube at a temperature sufficient to cause fusion and metallurgical bonding between the metal and the outside wall of said tube, and c. cooling the inside wall of said tube during the casting operation only in an area around the level of the molten metal in the ingot mold at a rate such that metallurgical bonding of the metal with the outside wall of the tube occurs while the inside wall remains intact at all times.
 3. The method of producing hollowing castings comprising the steps of: a. inserting an axial tube of compatible metal axially of a mold, said tube having an inside diameter substantially equal to the inside diameter of the hollow casting to be produced, b. inserting into the mold a sheet metal lining of the same material as the axial tube, c. pouring molten metal into the area between the mold and the tube at a temperature sufficient to cause fusion and metallurgical bonding between the metal and the outside wall of said tube, and d. cooling the inside wall of said tube at a rate such that metallurgical bonding of the metal with the outside wall of the tube occurs while the inside wall remains intact at all times.
 4. The method according to claim 3 wherein the axial tube is formed of a plating material different from the hollow casting to be produced and the mold includes a sheet metal lining of the same plating material as the axial tube.
 5. The method according to claim 1 wherein cooling gas is channelled through the inserted tube.
 6. The method according to claim 1 wherein cooling is applied by using a liquid cooling medium.
 7. The method according to claim 6 wherein water is used as cooling medium.
 8. The method according to claim 1 wherein the inserted tube is cooled during the casting operation only in an area around the level of the molten metal in the ingot mould.
 9. The method according to claim 1 wherein the molten metal is centrifuged in the ingot mould.
 10. The method according to claim 1 wherein the molten metal is centrifuged in the ingot mould from the beginning of the pouring operation.
 11. The method according to claim 10 wherein the melt is centrifuged around a vertical axis.
 12. The method according to claim 10 wherein the melt is centrifuged around a generally horizontal axis.
 13. The method according to claim 12 wherein the molten metal is channelled into the rotating ingot mould through a pouring spout onto the inserted tube.
 14. The method according to claim 1 wherein the ingot mould is covered up after completion of pouring and tilted into a horizontal position.
 15. The method according to claim 1 wherein the axial tube is held under tension during the entire casting process. 